silurid^. 



13. MOCHOCUS. 



Joannis, Mag. Zool. 1835, iv. ; Giinther, Cat, Fish. v. p. 217 (1864) ; Boulenger, Ann. & Mag. 



N. EL (7) vi. 1900, p. 525. 

 Rhinoglanis, Giinther, t. c. p. 216. 



Body moderately elongate, slightly compressed. Anterior dorsal fin ending over the 

 ventrals, formed of a strong spine and 6 to 8 branched rays ; a second dorsal, formed 

 of soft rays *, above the short anal fin. Pectoral fin with a strong spine ; ventral fin 

 with 7 rays. A cephalo-nuchal bony shield. Mouth subinferior, small, without labial 

 folds ; small conical teeth in both jaws, none on the palate. A maxillary and two 

 mandibular barbels on each side, the latter branched. Nostrils rather remote from 

 each other, both with a valve, the posterior very large. Eye moderate, without free 

 border. Gill-openings small, confined to the side. Air-bladder large, free. 



The skeleton is very similar to that of Synodontis. The nuchal shield is formed 

 of two transverse bones, with a small one on each side of the base of the dorsal fin. 

 The vertebrae number 34 (11 + 23) in M. niloticus, 33 (11 + 22) in M. brevis. 



This genus is represented by two species, both inhabiting the Nile, which may 

 easily be distinguished by the following characters : — 



M. niloticus. First dorsal fin much nearer the end of the snout than the root of the 

 caudal fin, with the spine serrated in front and 7 or 8 soft rays. 



M. brevis. First dorsal fin nearly equally distant from the end of the snout and from 

 the root of the caudal fin, with the spine smooth in front and with 6 soft rays. 



1. MOCHOCUS NILOTICUS. 

 (Plate LXXVI. fig. 2.) 



Joannis, 1. c. pi. viii. ; Gunther, 1. c, and Petherick's Trav. ii. p. 239 (1869) ; Boulenger, 1. c. 



Rhinoglanis typus, Giinther, 11. cc. pp. 216, fig., and 237, fig. 



Rhinoglanis vannutellii, Vinciguerra, Ann. Mus. Grenova, (2) xix. 1898, p. 254. 



Depth of body four and one-third to five and two-thirds times in the total length, 

 length of head three and one-third to four and a half times. Head depressed, not or 

 but little longer than broad, rugose above, with a large, oval frontal fontanelle ; occiput 

 with a low, blunt keel, which is continued on the nuchal shield ; eye supero-lateral, 

 three to four and a half times in the length of the head, once and one-third to once 



* This second dorsal fin corresponds to the adipose fin of most Siluridse ; the rays are true articulated 

 rays, but, as in Clarotes, they are devoid of endoskeletal supports. 



